Jersey - The @Context annotation for injection. How does it work?

I've run into some interesting results with the Rules of Injection, here's what I've found:

public class TodoResource{
  @Context
  UriInfo uriInfo; // Set second
  public TodoResource(@Context UriInfo value){
    uriInfo = value; // Set first (makes sense)
  }
  @Context
  public void setUriInfo(UriInfo value){
    uriInfo = value; // Set third
  }
}

I hope this helps.

Use @PostConstruct method annotation:

import javax.annotation.PostConstruct;
import javax.annotation.PreDestroy;

@Path("foo")
public class AuthResource {
    @Context
    HttpServletRequest request;

    public AuthResource() {
        //request is null
    }

    @PostConstruct
    public void postConstruct() {
        //request is NOT null
    }

    @PreDestroy
    public void preDestroy() {
       //after rest method executing
    }
}

Jersey doesn't modify the class, but it creates it on every request from the client.

After the class constructor was invoked, the context fields are injected.
(Should you try to access those fields inside the constructor, they will be null)

In your case, the class wouldn't need a specific constructor, so just:

public TodoResource () {
    // in most cases the ctor stays empty.
    // don't do much work here, remember: the ctor is invoked at every client request
}

But inside methods (which represent web-resources) annotated with @POST, @GET, ... you would have access to context fields.